#![no_main]
#![feature(compiler_builtins_lib)]
#![no_std]

extern crate compiler_builtins;

mod vga_text;

use core::fmt::Write;

#[no_mangle]
pub extern "C" fn _start() -> ! {
    let mut stdout = vga_text::OStream::new();
    stdout.clear();

    write!(&mut stdout, "hello world!");

    panic!("i has panicing");

    core::iter::successors(Some(0), |n| Some(n + 1))
        .for_each(|n| write!(&mut stdout, "hello world {}!", n).unwrap());

    loop {}
}

#[panic_handler]
#[no_mangle]
pub extern "C" fn panic_handler(_info: &core::panic::PanicInfo) -> ! {
    let mut stderr = vga_text::OStream::new();
    stderr.set_state(vga_text::CharState::from_colors(
        vga_text::Color::LightRed,
        vga_text::Color::Red,
    ));
    stderr.clear();
    stderr.print(b"uff-os");
    stderr.set_row(10);
    stderr.set_state(vga_text::CharState::from_colors(
        vga_text::Color::White,
        vga_text::Color::Red,
    ));
    stderr.print_centered(b"<kernel panic>");
    stderr.set_row(14);
    let text = _info
        .payload()
        .downcast_ref::<&str>()
        .unwrap_or(&"no panic information is obtainable");
    stderr.set_state(vga_text::CharState::from_colors(
        vga_text::Color::Cyan,
        vga_text::Color::Red,
    ));
    stderr.print_centered(text.as_bytes());
    loop {}
}